1. Field of the Invention
The present invention relates, in general, to a method of rolling shaped steel members having flanges and an apparatus therefor, and more particularly to a method of rolling such shaped steel members as H-sectioned members, I beams and rails as products with no shifting of the web and which are very accurate in size; and an apparatus therefor.
2. Description of the Prior Art
Of the various kinds of shaped steel members having flanges, there are some which are rolled by a universal rolling mill having the vertical rolls arranged on both sides of the to-be-rolled material and the horizontal rolls spaced vertically above and below the material, with the spindles of all these rolls positioned within the same or nearly the same vertical section. One of the problems with the operation of such a universal rolling mill is the great difficulty in setting the center of width of the flanges at nearly the same level as the center the thickness of the web. Taking the rolling of an H-sectioned steel members for instance, as shown in FIG. 1, there is the possibility that in producing such members there will be a shifting of the web, by the distance .DELTA.L between the central line AA of width of the flanges and the central line BB of thickness of the web.
The following is an explanation of the cause of the shifting of the web using the rolling a H-sectioned steel member as an example:
FIG. 2 shows the rolling of an H-sectioned steel member 1 by the horizontal rolls 11, 12 of a universal rolling mill, wherein the vertical rolls are not shown for the purpose of simplification; and the H-section 1 is shown in the long direction. Numeral 15 denotes a roller table; Yv indicates the line indicating the position at which the vertical rolls start the reduction of the flanges 2 of the H-section steel member 1; and YH indicates the line indicating the position at which the horizontal rolls 11, 12 start the reduction of the web 3 of the H-sectioned steel member 1; and Y.sub.0 indicates the line running through the centers of the spindles of the horizontal rolls 11, 12. In the present invention, the distance between Y.sub.0 and Y.sub.H is called the projected contacting length l.sub.H of the biting by the horizontal rolls; and the distance between Y.sub.0 and Y.sub.V is called the projected contacting length l.sub.V of the biting by the vertical rolls. EQU If l.sub.H &lt;l.sub.V . . . (1),
the rolling of the H-sectioned steel member 1 will start with the reduction of the flanges 2 by the vertical rolls. Thus, the H-sectioned steel member 1 is gripped by the contacting of the vertical rolls with the outside of the flanges and also the contacting of the sides of the horizontal rolls with the inside of the flanges, so that it is held against movement vertically because of friction force produced between the member and the working rolls.
Then, the reduction of the web will start with the horizontal rolls 11, 12. In such a case, there is a deviation of the pass line C'C running parallel with the rolling direction through the center of the space between the horizontal rolls 11 and 12, from the line, B'B running through the center of width of the flange of the H-sectioned steel member, hereinafter called the central line of the flanges, and the web 3, which is initially lower than it should be as shown with the double hatching 6 on the left portion of FIG. 2, will be shifted during the rolling of such material higher than it should be, as shown with the double hatching 7 on the right portion of FIG. 2. Such phenomenon is called the "shifting of the web", which is the main cause of the production of "shifted webs".
In the case of the rolling of H-sectioned steel members by a universal rolling mill, it is difficult to adjust the arrangement of the working rolls of such universal rolling mill or the posture of the H-sectioned steel member before rolling, so that the line B'B running through the center of width of the flanges of the H-sectioned steel member may not remain level with the pass line C'C of the universal rolling mill throughout the rolling operations; therefore, it is possible that H-sectioned steel members having shifted webs as shown with the double hatching 7 in FIG. 2, are produced.
A guide shoe of a conventional type has been devised which holds the web of the H-sectioned steel member between its hands and guides the web so that the center of the thickness of the web is level with the pass line of the universal rolling mill. In the case of the rolling of such members having already shifted webs, however, such webs are sent into rolling operation with the web shifted so the shifted web remains in the finished H-sectioned steel members.
In order to prevent the shifting of the web, there has been proposed the following device:
Referring to FIGS. 3 and 4, an arrangement used in the rolling of an H-sectioned steel member 1 having flanges 2 by a universal rolling mill having vertical rolls 13, 14 and horizontal rolls 11, 12 with all their spindles positioned within the same or nearly the same vertical section, has the biting position Y.sub.H for the horizontal rolls nearly coinciding with or preceding he biting position Y.sub.V for the vertical rolls. This is accomplished by adjusting the ratio of the diameter of the vertical rolls and the horizontal rolls and additionally by adjusting the reduction carried out in the rolling pass, thereby preventing the shifting of the web. However, the arrangement is not effective in the case of rolling materials having shifted webs, such as H-sectioned steel members in which the center of thickness of the web 3 is shifted from the center of width of the flanges 2, so that rolling operations are effected without correction of such shifting of the web. In other words, to-be-rolled materials should be free of the shifted web before being put into rolling operation. Another problem with the arrangement is that there is the possibility of irregular spread of the width of the flanges at points f.sub.1 -f.sub.4 in FIG. 1 due to irregularity of reduction and temperature distribution, such irregular spread, particularly the difference between the upper and the lower portions of the flange from its center, making it impossible to correct the shifting of the web during rolling operations, resulting in the production of products with shifted webs.
Besides the abovementioned arrangement, there has been devised another device, according to which without regard to the biting position of the horizontal rolls and the biting position of the vertical rolls on the flanges, means is provided that applies a pair of forces that work counter to each other in a vertical section to the upper and the lower edges of the respective flanges at an appropriate position before the space between the working rolls with continuous change of strength according to the shifting of the web from the theoretically ideal position for the center of its width, so as to act on the edges upwards or downwards within the vertical section. The means of this device is constituted by guide rolls or means having the same function as such rolls between which the to-be-rolled material is placed just before the space between the working rolls as the material is bitten into by the working rolls, and to move said guide rolls or the like means are moved up or down, thereby subjecting the web of the material to a bending force.
However, this device has a problem that in order to set the center of thickness of the web at the center of width of the flange, there are used only a pair of forces working counter each other and acting vertically upwards or downwards, and such forces, accordingly, are required to be very strong, so that the rolling apparatus using such device must be largesized, resulting in a great economical disadvantage. The apparatus also must have a complicated construction, because such forces move continuously up or down within one and the same vertical section, requiring a great amount of labor for maintenance, which constitutes another disadvantage of the device. Also, when using the device, it is necessary to adjust the bending force to meet the changing shift of the web, making it necessary to use a detector of the position of the hot steel members for continuous detection of their position. However, there have not yet been commercialized any detectors that can satisfy all the technical requirements, including the sufficiently high accuracy of detection. Even if such detector is developed, it will only be with great difficulty and at great cost.